This study concerns the use of antiemetics to control nausea and vomiting for patients undergoing I-131 therapy for follicular and papillary thyroid cancers. We attempted to determine if the intervention of prophylactic antiemetics makes a significant difference between the control and intervention groups for the outcomes of nausea and vomiting. The anticipated benefits of this would include: 1) the prevention of nausea and vomiting with a secondary advantage of insuring complete dosing of the I-131. When vomiting occurs post I-131 dose, the full prescribed and calculated dose of I-131 can not be recovered for re-dosing. 2) increased patient comfort 3) maintenance of a safe environment for staff as vomiting creates radiation hazards to staff who must care for the patient . Reducing vomiting represents reasonable measures to maintain radiation exposures as far below the level as is reasonably achievable (ALARA). 4) better hydration which is required for prevention of bladder complications caused by retention of I-131 in the urinary tract. The design of this study utilized a prospective intervention and control methodology ( Stanley and Cambell ,1963). Patients were randomly assigned into an intervention or control group to receive compazine or placebo. Both groups received a blinded "study drug" prior to I-131 and then every 6 hours for 2 days. Nausea and vomiting were evaluated both subjectively and objectively on a regularly scheduled basis. 24 patients completed the study and statistical analysis is currently in process. There were no side effects to the compazine and only one patient withdrew prior to completion.